1. FIELD OF THE INVENTION
This invention is concerned with composition and methods for combatting coccidiosis and improving weight gain in warm-blooded animals, having been exposed to or infected with coccidia parasites, by subcutaneous administration of implants which are slow-release forms of certain ionophores, the polycyclic ether antibiotics including salinomycin, 4-methylsalinomycin, monensin, nigercin, grisorixin, disnerycin and lasalocid.
Uncontrolled development of the coccidia parasite in certain warm-blooded animals, excluding man, can debilitate the animal and aggravate other diseases present. Infection with coccidia in one animal can readily be spread throughout the entire group, such as sheep and cattle in the feed lot and pasture, chickens in pens, and canine and feline species of animals through excretion of coccidia oocysts and subsequent ingestion by uninfected animals. According to the present invention, sustained release or small amounts of certain ionophores from an implant administered beneath the skin of warm-blooded animals supplies a steady supply of a small amount of the ionophore to the bloodstream. Transported by the blood to certain coccidia reproduction sites, the ionophores interfere in the life cycle of the parasite, particularly in development of coccidial sporozites, trophozites and immature schizonts. Interference in these stages in the development of coccidia parasites kills a large percentage of these organisms and the number of oocysts excreted is thereby reduced which reduces spread of coccidiosis. 2. DESCRIPTION OF THE PRIOR ART
Subcutaneous implantation of slow release forms of polycyclic ether antibiotics to control coccidiosis in warm-blooded animals has heretofore been unknown. Oral administration of these antibiotics such as salinomycin (U.S. Pat. No. 3,857,948) is used to control coccidiosis in poultry. Slow release forms of drugs and antibiotics for treatment of certain microbial diseases as subcutaneous implants in animals have been disclosed, such as micro-encapsulated biodegradable forms described in U.S. Pat. No. 3,773,919 wherein the matrix for holding medicinals useful as implants is a formulation of polylactide polymer. The coccidia parasite, however, is a class of protozoa living in the cells lining the intestines of animals and control of such parasites in animals via medication absorbed through the blood from a subcutaneous implant was unknown until the present invention.